A 61-year-old woman presented with a 3-month history of leg swelling and back pain. Imaging revealed a large retroperitoneal mass with hydronephrosis. A diagnostic procedure was performed, and management decisions were made.

This case was presented at the Cancer Center Grand Rounds.

Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.

We thank Dr. David Ryan for his help in organizing the conference.

Source Information

From the Departments of Hematology–Oncology (E.P.H., Y.-B.C.), Internal Medicine (M.F.B.), Radiation Oncology (K.M.W.), Radiology (V.V.M.), and Pathology (A.L.), Massachusetts General Hospital, and the Departments of Hematology–Oncology (E.P.H., Y.-B.C.), Internal Medicine (M.F.B.), Radiation Oncology (K.M.W.), Radiology (V.V.M.), and Pathology (A.L.), Harvard Medical School — both in Boston.